How can I set different RF Gain for the second antenna in diversity mode?

Howard K7JNX · January 2022

Here's the situation: I have a 6600 with a receive-only magnetic loop attached to RXB with my normal antennas attached to ANT1. The magnetic loop needs 32db of RF gain.

If I start with Slice A attached to ANT1, then click the DIV button, it opens up Slice D with ANT2 (nothing attached there). I then click to change Slice D to RXB but the slice D signal is weak because of the need for RF gain. But if I click ANT in an effort to change the RF gain of RXB, it does not show up - it only allows me to change the RF gain of ANT1, ANT2, RXA, XVTA or XVTB. It does not show an option to change the gain for RXB and the second SCU.

A clumsy workaround seems to be as follows: Open a second panadapter (which presumably uses the second SCU), delete the two slices on it, and then select its ANT button and then change the RF gain of RXB to +32db.

What is a non-clumsy way to set a different RF gain for the second antenna in diversity mode? In other words, how can I independently set the RF gain for the two SCUs?

Mike-VA3MW · January 2022

Hi Howard

Give this a try https://www.flexradio.com/insider/interview/qa-with-ken-buser-rxassistant/

73

Howard K7JNX · January 2022

Thanks for the pointer to RXassistant, Mike. I've installed it and played around with it, but it does not seem to provide a way to answer my question. While it does allow me to change antennas for slices A and B, and even to invoke diversity mode with slices A and D, it only seems to allow a single RF gain adjustment -- not the separate and different RF gains that I need.

Ignacy · January 2022

I don't know how to do it but have workarounds.

First, the Flex is is pretty good in handling overload. So with +24 db gain the transmit antena may only need an AGCT adjustment. I think the improvement in NF from 24 to 36 db is very small.

Second, you may need a better amp for your receive antenna. Flex has a preamp but noisy with NF around 10 db. A preamp would be better. I use DX Eng preamp with NF around 2 db for my beverages. While the preamp is not strictly needed for 160m and 80, it is needed for 40 and essential for 20m.

Ignacy NO9E

Howard K7JNX · January 2022

Thanks for the comments and suggestions, Ignacy.

My loop is in fact a Pixel RF-Pro-1B but its preamp is dead. I've found that the antenna works amazingly well if I bypass the dead remote preamp and feed directly into the Flex 6600 RXB port if I crank the RF Gain up to +32db. So I'm reluctant to spend $200 to replace the Pixel preamp since the 6600 preamp works surprisingly well. Hence my original question about a non-clumsy way to set RF Gain for a slice using RXB to one value (+32db) while setting a different (+0db) for a slice using ANT1.

Larry _ NY8T · January 2022

Since there is no way yet to actually steer diversity in SmartSDR, why not just open up a second panadapter with a slice on the same frequency and ant2 or RX2 like you mentioned, then you can adjust your preamp independantly for ant1 and ANT2/RX1/RX2. If you want the 2 slices to track togeather FrStack has this capability. This is the only way I can see to do what you want.

How can I set different RF Gain for the second antenna in diversity mode?

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